This technique is notably described in the document “Influence of admixture on the properties of porous and draining cement concrete” (Matériaux and Constructions, vol. 33, December 2000, pp 647-54). The Applicant indicates that through use of the term “granulates” the intention is to designate according to the term well known to the skilled man in the art fillers, fine sands, sands, gravel-sands mixtures, chippings, ballasts and their blends, as defined by French norm XP P 18-540 (the said norm in fact classifies these materials on the basis of a number of characteristics such as the size of the grains or the granular class, the fines content, the fineness module, cleanliness, indices of crushing, if applicable, sensitivity to freezing temperatures, hardness, etc.; characteristics which it is not essential to list here).
The rheological additive used in the course of this process must give the formulation a number of properties, in each of the stages characterising this process.
During stage 1) of blending, it is desirable that the formulation should have an excellent “fluidity”; this fluidity determines the uniform distribution of the different constituents in the blend. This fluidity leads to a low viscosity of the formulation during this stage.
After blending, i.e. during stage 2), the viscosity of the formulation must increase.
During stage 3) of introduction of the formulation into the mould, it is desirable that the said formulation should have a satisfactory “flow”: this flow reflects the ability of the said formulation to be poured out continuously in the mould, without its viscosity increasing too greatly: this could notably obstruct the pipes through which the formulation transits before being introduced into the mould, or alternatively prevent complete filling of this mould, which ultimately leads to surface defects of the part thus manufactured. With a view to obtaining a satisfactory flow the viscosity of the formulation must be greatly reduced during this stage. In addition, this reduction must be as rapid as possible, since the operation of introducing the formulation in the mould lasts only a few seconds.
During stage 4) of vibrocompaction, in which the formulation is subject to substantial shearing stresses (vibration action) and pressure stresses (compacting action), an excellent “fluidity” is sought, which takes the form during this stage of a low value of viscosity of the formulation:                which enables the formulation to follow perfectly the inner surface of the mould into which it is introduced, firstly, without which defects on the surface of the end part might be observed,        and which enables within the mould a material to be obtained having excellent compactness, secondly, leading to an improvement of the mechanical resistance properties of the end part.        
The Applicant stipulates that this compactness reflects at once a uniform distribution of the different constituents of the formulation within the mould, together with a reduced porosity within the end part, and also a reduced number of macroscopic defects (such as areas with high concentration of binder, or of granulates, when the latter are present in the formulation). Secondly, since the stages of introduction in the mould and of vibrocompaction last only a few tens of seconds, it is very important that the viscosity of the formulation should rapidly change from a high-value (condition at rest) to a low value (stages of introduction into the mould and of vibrocompaction).
Finally, following operation 5), removal from the mould, it is desired that an end part having the following characteristics is obtained:                “non-adhering”, i.e. one which does not adhere to the internal walls of the mould, in order not to create surface defects,        and “cohesive”, i.e. it retains the compactness which it has acquired during the vibrocompaction stage: the attempt is then made to obtain as rapid an increase as possible of the viscosity of the formulation, with a view to obtaining cohesion of the end part as rapidly as possible.        
Thus, all these properties may be summarised by:                a high viscosity of the formulation in the absence of stress (stages of rest and of removal from the mould),        a low viscosity of the said formulation in the presence of a high shearing stresses (stages of blending, of introduction of the formulation into the mould and of vibrocompaction),        a very rapid change from a low viscosity under high shearing to a high viscosity under low shearing for this formulation, and vice versa,        a non-adhering and cohesive appearance of the end part when removed from the mould,which will henceforth be qualified as the “complex technical problem” resolved in the present Application.        
Continuing its research with a view to improving all these properties, the Applicant has developed the use of a rheological additive, in a process of manufacture by vibrocompaction of a water-based formulation and of at least one hydraulic binder, characterised in that the said additive is an emulsion of at least one non-cross-linked copolymer consisting:                a) of (meth)acrylic acid,        b) of alkyl(meth)acrylate having 1 to 25 carbon atoms, in which this alkyl methacrylate is preferentially ethyl(meth)acrylate,        c) of a monomer of formula R1—(R2O)m—R3, in which:        R1 designates a radical containing an unsaturated polymerisable function, belonging to the group of vinylics, or to the group of acrylic, methacrylic, maleic esters, or to the group of unsaturated urethanes such as acrylurethane, methacrylurethane, α-α′ dimethyl-isopropenyl-benzylurethane, allylurethane, or to the group of allylic or vinylic ethers, whether or not substituted, or again to the group of ethylenically unsaturated amides or imides, or again to the group constituted by acrylamide and methacrylamide, and preferentially methacrylic,        R2O designates an alkylene oxide group having 1 to 6 carbon atoms, preferentially an ethylene oxide and propylene oxide group, and very preferentially an ethylene oxide group,        m is an integer between 20 and 30, preferentially between 23 and 27, and is very preferentially equal to 25,        R3 designates a linear or branched alkyl chain having 28 to 33 carbon atoms, preferentially 30 to 33 carbon atoms, and very preferentially having 32 carbon atoms.        
An examination of the state of the technique with a view to resolving the “complex technical problem” forming the subject of the present Application will demonstrate that none of the documents accessible to the skilled man in the art reveals or suggests the solution forming the subject of the present invention.
The skilled man in the art is familiar with document U.S. Pat. No. 6,573,326, which describes thickening agents with a base of partially saponified vinylic alcohol copolymers, able to be used in the manufacture of dies containing a hydraulic binder. This document reveals measures for spreading a cement composition, implemented after vibration of the said composition: the thickening agent according to the invention enables the value of the spreading to be reduced.
The skilled man in the art is also familiar with document US 2005/011416, which describes the use of a pair consisting of a thickening agent and a hydrophobic additive, in the manufacture of cement-based articles, notably through the vibrocompaction method. The thickening agent is chosen from among the carboxylic acids, the poly(meth)acrylates, polyurethanes, polyethers, alginates, polyoses, polyimines, polyamides, cellulose derivatives, silicic acid, while the hydrophobic additive is chosen from among the (hydro)silanes, the siloxanes, the silicons, the siliconates, the fluorosilicates, the fatty acids, the waxes, the epoxide, acrylic or polyurethane resins, the sodium silicates and the esters of silicic acid. It is indicated that when manufacturing a cement part by vibrocompaction, the use of this pair enables a uniform end product to be obtained, which does not adhere to the mould, and which has a satisfactory mechanical resistance.
Document FR 2 836 141 is also well-known; compared to the previous documents it draws the attention of the skilled man in the art to a certain type of polymers, which enable cement products manufactured by vibrocompaction to be given advantageous performance characteristics. These polymers consist of (meth)acrylic acid, alkyl (meth)acrylate acid, and of a third monomer having a polymerisable group, which is terminated by a fatty and/or hydrophobic chain. The operating mechanism of such polymers is not addressed in this document; it will be explained in detail when the teaching of document US 2006/054056, which gives a detailed explanation of this mechanism, is discussed.
Thus, document FR 2 836 141 describes compositions with a base of extrusible or pressable hydraulic binders, in which the water/binder ratio is less than or equal to 0.25, and containing a rheology agent consisting of methacrylic acid, an alkyl methacrylate which is preferentially ethyl(meth)acrylate, and of a third monomer including a polymerisable unsaturated group and a chain of the following type:—COO—(RtO)m—Rz or —CO—N(Rp)—(RtO)m—Rz                 where Rz is a linear or branched alkyl group having 1 to 35 carbon atoms,        Rt is an alkylene group having 1 to 6 carbon atoms,        Rp is H or an alkyl group having 1 to 8 carbon atoms,        m is between 1 and 50.        
The examples and the claims of this document demonstrate that the preferred added monomers have chains having 5 to 35 ethoxylated units and a hydrophobic grouping having 18 to 35 carbon atoms, the most preferred added monomers being behenyletherpolyethylene glycol methacrylate and methoxypolyethylene glycol methacrylate having 10 to 35 ethoxylated units. The advantages procured by such polymers are improved mechanical performance, improved compactness and an absence of surface defects.
However, none of the 3 previous documents (U.S. Pat. No. 6,573,326, US 2005/011416, FR 2 836 141) seeks to resolve the “complex technical problem” forming the subject of the present Application. The Applicant indicates that the document acting as the closest state of the technique is document US 2006/054056. This document teaches the use, notably in the manufacture by vibrocompaction of parts containing a hydraulic binder, of different chemical additives which are, notably, associative polymers.
The Applicant wishes to indicate that the action mechanisms and the characteristics of the associative thickening agents, such as the associative thickening agents of the HASE (hydrophobically alkali swellable emulsions) type, are now well known, but have been essentially described in a field far removed from that of the present Application: that of paints. One can, for example, refer to the documents “Rheology modifiers for water-borne paints” (Surface Coatings Australia, 1985, pp. 6-10) and “Rheological modifiers for water-based paints: the most flexible tools for your formulations” (Eurocoat 97, UATCM, vol. 1, pp 423-442). These associative thickening agents are water-based polymers having insoluble hydrophobic groupings. Once such molecules are introduced into water, the hydrophobic groupings which they contain tend to assemble in the form of micellar aggregates. These aggregates are linked together by the hydrophilic parts of the polymers: there is then formation of a three-dimensional network which causes the viscosity of the medium to be increased. In the presence of a stress, destruction of the three-dimensional network occurs, and a reduction of the viscosity of the medium is observed.
As indicated in document US 2006/0054056, such polymers do not develop any thickening properties in the presence of shearing: the formulation is therefore very fluid during the vibrocompaction stage, which improves its compactness (reduction of porosity, of the number of macroscopic defects, uniform distribution of the constituents of the formulation). When the stress ceases the associative thickening mechanism develops, and a perfectly cohesive formulation is obtained, which enables its compactness to be retained, and an improved compression resistance to be acquired.
Thus, the purpose of document US 2006/0054056 is indeed to obtain a satisfactory flow of the formulation within the mould, a satisfactory fluidity of the said formulation during vibrocompaction, and a non-adhering and cohesive appearance of the end part on removal from the mould: no parts glued on to the inner walls of the mould are observed, nor surface defects of the manufactured part. It will, however, be noted that the complex technical problem forming the subject of the present Application is only partially resolved: indeed, document US 2006/0054056 does not seek to improve the rapidity of the transition between a low viscosity under high shearing and a high viscosity under low shearing, and vice versa. However, this is a fundamental property for the skilled man in the art, since it characterises the ability of a formulation rapidly to acquire a high degree of cohesion (when the part is removed from the mould), and its ability to be rapidly used in the mould (during filling and vibrocompaction). As will be seen below, not only does document US 2006/0054056 not seek to resolve this problem, but the particular polymers which it reveals do not enable this problem to be resolved.
The polymers used in this document are essentially thickening agents used in the field of paints, such as traditional acrylic thickening agents such as Carbopol™ (NOVEON™), or acrylic associative thickening agents belonging to the Aquaflow™ (HERCULES™), Acrysol™ and Acusol™ (ROHM & HAAS™) ranges, the preferred products, and those used in the examples, being Acrysol™ TT 935 (3 examples out of 4) and to a lesser degree Carbopol™ Aqua 30 (1 example out of 4). Acrysol™ TT 935 is a product consisting of methacrylic acid, ethyl acrylate acid, and an added monomer having a polymerisable function, having a link with 20 oxyethylated units and a fatty chain having 18 carbon atoms. Carbopol™ Aqua 30 is a cross-linked acrylic thickening agent.